ERBB2 and gastric cancer: The PI3K/AKT/mTOR pathway is frequently altered in GC.108,167 From the TCGA molecular subtypes, most of the GC cases studied had different degrees of mutations in the PIK3CA gene and amplification of RTK genes such as EGFR and HER2. 41,168,169 Mutations of the PIK3CA gene are likely to be late and isolated events in GC.95,170 The relationship between PIK3CA mutation and the prognosis of GC patients is controversial.